The foreign body response to medical devices and materials implanted in the human body, including scarring, fibrous encapsulation and potential rejection, is a longstanding and serious clinical issue. There are no widely acceptable or safe therapies for ameliorating the foreign body response. Clinical complications resulting from the response include disfigurement of silicone prostheses and loss of function of devices such as implanted pacemakers, stents, and shunts. Cellularized implants and stem cells placed in the body are also subject to the foreign body response with the added issue that the regenerative repair intended to be prompted by the graft may be inhibited. Beneficial modification of the body's reaction to implanted materials, medical devices, engineered constructs or stem cells would be a fundamentally important therapeutic advance. We have recently reported the use of a peptide based on the Cx43 carboxyl terminus (CT) that reduces inflammation, scarring and myofibroblast differentiation associated with cutaneous wounds and sub-dermal placement of a silicone implant in rodent and porcine models. Our data are consistent with growing evidence for key roles of the gap junction protein Cx43 in wound response and tissue repair processes (Rhett et al., 2008). In this application it is our hypothesis that disruption of the function of Cx43 reduces scarring and improves regenerative integration of implanted materials, including cellularized constructs via Cx43-mediated effects on TGF-beta signaling. We will test this hypothesis in 3 aims: First, by determining the mode of action of the Cx43 CT peptide in reducing scarring and promoting tissue regeneration and comparing its mechanism and actions to another Cx43-function-targeting approach based on Cx43 shRNA. Second, by determining and comparing the efficacies of the Cx43 CT peptide and Cx43 shRNA in ameliorating the foreign body response to sub-dermal placement of a simple silicone implant and a collagen-based 3D implant containing progenitor cells designed to regenerate skeletal muscle. And third, the efficacy of the two Cx43 targeting approaches in enabling regenerative repair of muscle by the device in the mechanically active muscles of the abdomen. It is our objective to characterize and establish the usefulness of targeting Cx43 function as a strategy for improving the biocompatibility of medical implants.